1. Field of the Invention
The present invention relates to a method of automatically stripping off an insulating coating of an insulated electric wire at an intermediate portion in a longitudinal direction thereof.
2. Description of the Related Art
Referring to FIGS. 18 to 21, a conventional method of stripping an insulated electric wire will be described below.
This method of stripping the electric wire is to remove an insulating coating 1a at an intermediate portion of an electric wire 1 in a longitudinal direction. First of all, as shown in FIG. 18, circumferential cuts are formed in the insulating coating la of the electric wire 1 at two positions which are separated in a longitudinal direction from each other, by means of two pairs of circumferentially cutting cutters (hereinafter referred to as xe2x80x9ccircumferential cuttersxe2x80x9d) 55-58 each located vertically or laterally. Each of the circumferential cutters 55-58 has cutting edges 59, 60 substantially in V shape as seen in FIG. 19. The insulating coating 1a is cut substantially in a rhombic shape to leave portions 40-43 uncut (connected parts) above and below as well as at the left and the right of a core 1b. 
Then, as shown in FIGS. 20A and 20B, a pair of left and right longitudinally cutting cutters (hereinafter referred to as xe2x80x9clongitudinal cuttersxe2x80x9d) 63, 64 are positioned in a vertical direction below the insulating coating 1axe2x80x2 between the forward and backward circumferential cuts 61, 62. The electric wire 1 is pressed by a ultrasonic horn 28 from the above toward the longitudinal cutters 63, 64 with ultrasonic vibrations to form longitudinal cuts at both sides of the insulating coating 1axe2x80x2. A distance between a pair of the cutters 63, 64 is substantially equal to an outer diameter of the core 1b of the electric wire 1. With this operation, the insulating coating 1axe2x80x2 is divided into an upper and a lower parts between the forward and backward circumferential cuts 61, 62. At the forward and backward circumferential cuts 61, 62, the insulating coatings 1a, 1axe2x80x2 (FIGS. 20A and 20B) are not separated but connected as shown in FIG. 19 above and below as well as at the left and the right of the core 1b. 
Finally, as shown in FIG. 21, the upper and the lower insulating coatings (waste coatings) 65, 66 are manually removed by an operator by pulling them from the electric wire 1 in upward and downward directions. By pulling the insulating coating 1axe2x80x2 (FIGS. 20A and 20B) in the upward and downward directions, the connected parts 40-43 (FIG. 19) of the insulating coatings 1a, 1axe2x80x2 above and below as well as at the left and the right are completely cut away. The waste coatings 65, 66 are dropped on a bottom of a stripping machine (not shown) in situ and gathered by the operator afterward for a cleaning treatment.
To the core 1b exposed at the intermediate position of the electric wire 1 as shown in FIG. 21 is connected an end portion of another electric wire (not shown), for example, by means of a joint terminal or welding for branching. Alternatively, a positioning terminal (not shown) is press fitted to the core 1b, and the electric wire 1 is positioned and fixed in a longitudinal direction inside a connector housing which is not shown.
However, in the above described conventional stripping method for an insulated electric wire, the operator must remove the waste coatings 65, 66 from the electric wire 1 by hand. Therefore, the conventional method has had such a problem that a productivity is low because it takes a number of working steps, and a problem in quality because the removal of the waste coatings 65, 66 are likely to be forgotten. There is another problem that after the circumferential cuts are formed in the insulating coating 1a, the electric wire 1 is likely to slacken, which incurs inaccuracy in forming the longitudinal cuts in the later steps. In such a case, the removal of the insulating coating 1a cannot be done well and cut faces of the insulating coating 1a get ugly, which results in a problem of quality. Further, because the insulating coating la is removed by hand in a manner of tearing it off, the cut faces of the insulating coating 1a are likely to chap, which also results in a problem of quality. Moreover, such cleaning work by the operator that he must gather the waste coatings 65, 66 which have fallen on the bottom of the stripping machine has been very annoying.
Therefore, it is an object of the present invention to provide a method of stripping an electric wire in which an insulating coating can be automatically removed (peeled) reliably and beautifully, and a reduction of the working steps and improvements in productivity as well as in quality can be attained.
In order to attain the above described object, a gist of the invention resides in a method of stripping an electric wire in which circumferential cuts are formed in an insulating coating of the electric wire by means of circumferential cutters, and then longitudinal cuts are formed in the insulating coating by means of longitudinal cutters to remove the insulating coating, comprising the steps of moving the circumferential cutters in a longitudinal direction of the electric wire in a state where the circumferential cuts have been formed in the insulating coating by means of the circumferential cutters, and disconnecting cut pieces of the insulating coating from each other at those parts where the circumferential cuts are formed.
According to another feature of the invention, pairs of wire clamps are arranged at both sides of pairs of the circumferential cutters, the circumferential cutters conducting, in a state where the one pair of the wire clamps hold the electric wire and the other pair of the wire clamps are released, a first movement toward the other pair of the wire clamps, the circumferential cutters then conducting, in a state where the other pair of the wire clamps hold the electric wire and the one pair of the wire clamps are released, a second movement toward the one pair of the wire clamps along a distance longer than the first movement.
According to a further feature of the invention, after the circumferential and longitudinal cuts have been formed in the insulating coating respectively by means of the circumferential cutters and the longitudinal cutters, the insulating coating is removed by an air blow and waste coatings can be sucked by a vacuum.
According to a still further feature of the invention, when the longitudinal cuts are formed in the insulating coating by means of the longitudinal cutters, longitudinally cut edges of the insulating coating are adapted to abut against shoulders which continue by intersecting with inclined outer faces of cutting edges of the longitudinal cutters respectively.
According to a still further feature of the invention, a lower portion of the waste coating is dropped by its self weight between a pair of the longitudinal cutters.
There is further provided a method of stripping an electric wire in which circumferential cuts are formed in an insulating coating of the electric wire by means of circumferential cutters, and then longitudinal cuts are formed in the insulating coating by means of longitudinal cutters to remove the insulating coating, comprising the steps of forming the longitudinal cuts in the insulating coating by means of the longitudinal cutters, and abutting longitudinally cut edges of the insulating coating against shoulders which continue by intersecting with inclined outer faces of cutting edges of the longitudinal cutters respectively.
According to a further feature of the invention, the insulating coating is removed by an air blow in a state where the longitudinally cut edges of the insulating coating have abutted against the shoulders.
According to a still further feature of the invention, the insulating coating of the electric wire is pressed toward the longitudinal cutters while making ultrasonic vibrations by means of a ultrasonic horn.
The above and other objects, features and advantages of the invention will become more apparent from the following detailed description of a preferred embodiment taken in connection with the accompanying drawings.